Some of the Global Navigation Satellite System (GMSS) antennas in the market today rely on a technology called a patch antenna. This antenna is structured as a metal “patch” of some shape (rectangular, square, circle, triangle) located above a ground plane with a dielectric material in between the metal parts.
The patch is generically sized to about half a wavelength (dielectric compensated) at the center frequency of desired band. These patches can be excited through a variety of feeding methods: micro strip, probe or aperture coupled, to name a few. Patch antennas are generally limited to 10-20% bandwidth.
Thus, to cover the entire Global Navigation Satellite System (GNSS) spectrum, from 1164 MHz and up to 1610 MHz, it is common to stack patches with different resonant frequencies. This offers the advantage of keeping the horizontal phase center (the virtual point in space that the GNSS system measures its range) between the different bands in the location. This allows the location being measured to be independent of the orientation of the antenna.
However, stacking the patches has the disadvantage of requiring more effort to manufacture as the feeds of the upper patch should pass thru the lower patch and the feeds for the lower patch should terminate below the upper patch.